Smirnov, V.L. Vorozhtsov, S.B. JACoW Geneva, Switzerland 978-3-95450-167-0 10.18429/JACoW-Cyclotrons2016-WEB04 English 270-273 WEB04 cyclotron ion injection extraction acceleration Contribution to a conference proceedings 2017 2017-01 http://dx.doi.org/10.18429/JACoW-Cyclotrons2016-WEB04 http://jacow.org/cyclotrons2016/papers/web04.pdf A concept of coupled cyclotrons for acceleration of carbon ions (charge 6+) to 400 MeV/nucleon by a separated sector cyclotron consisting of six sector magnets with superconducting coils is proposed. Injection to the machine will be provided by a compact 70 MeV/nucleon cyclotron. The accelerator complex is intended for setting up a radiation therapy facility employing carbon ions. The advantages of the dual cyclotron design are typical of cyclotron-based solutions. The first design studies of the sector magnet of the main cyclotron (magnetic field increases from 4.2 T to 6.5 T, RF frequency 73.56 MHz, RF mode 6) show that it is feasible with acceptable beam dynamics. The accelerator has a relatively compact size (outer diameter of 8 m) and can be an alternative to synchrotrons.